JP2002372496A - Outer shape inspection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an outer shape inspection system for inspecting an outer shape by reading the image of the detection site in a work speedily and accurately. SOLUTION: At the upstream side of a CCD camera 2 having inherent focus distance, first the amount of deviation of the passage position of the detection side of a work W being carried is detected by a displacement detection sensor 5. By a signal from the displacement detection sensor 5, a traveling apparatus 4 is driven, the CCD camera 2 is moved according to the amount of deviation, and the focus position of the CCD camera 2 is adjusted so that the detection site of the work W passes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a visual inspection system for performing image processing on a detected portion of a conveyed work and performing visual inspection.

[0002]

2. Description of the Related Art In a visual inspection system, an image is generally captured using a CCD camera (imaging device), the image is processed, and a visual inspection is performed based on the detected image. . Then, as a method in which the CCD camera forms a detection image at a focal position,
Fixed focus method with a fixed focal length, and autofocus (automatic focusing of the lens) that detects the distance to the subject using an electronic device and adjusts the focal length to focus.
The method is known.

In such a visual inspection system, there is a demand for speeding up the inspection, that is, performing the inspection while transporting the work. In addition, when the work is a blade, it is necessary to inspect the vicinity of the ridgeline of the blade for scratches, defects, and adhesion of foreign matter by image processing. The accuracy of the inspection is on the order of μm. Is required.

[0004]

However, when the inspection is performed at high speed and with high accuracy by using the above-mentioned fixed focus type CCD camera, there are the following problems.

[0005] The higher the magnification of a CCD camera, the shallower the depth of field becomes, and the CCD camera is in focus due to a change in the distance between the imaging device and the detected part of the work (for example, the surface shape of the detected part of the work). A so-called out-of-focus state occurs in which the image is taken without being taken. When such an out-of-focus state occurs, image processing of a captured image cannot be performed with high accuracy, and as a result, an appearance inspection for determining the quality of the appearance of a work cannot be performed with high accuracy. Further, since the inspection is performed over the entire length in the longitudinal direction of the blade, if the depth of field of the imaging device is smaller than the standard dimensional tolerance of the blade, the image itself cannot be detected.

On the other hand, if an autofocus type CCD camera is used instead of the fixed focus type CCD camera, the following problems occur.

[0007] The auto-focusing method performs auto-focusing as described above, and the focusing requires a certain amount of time. Therefore, when performing inspection over the entire length of the blade, in addition to the photographing time, the auto-focusing method is required. In addition, it is necessary to secure extra adjustment time required for automatic focusing, which is disadvantageous in performing inspection at high speed.
In addition, since a spot that serves as a reference for the focusing is necessary for automatic focusing, when a work is a blade, it is possible to photograph a corner (line) such as a ridge edge of the blade obliquely. Have difficulty.

Therefore, the inventor of the present invention first makes a fixed focus type imaging device (for example, CC
D camera), the work detection site (surface)
When passing through the focal position of the imaging device, it can be said that the subject is in focus if it is within the depth of field. If not,
If the position of the workpiece is adjusted by moving the imaging device itself, it can be easily corrected so that the detected portion of the workpiece passes through the focal position of the imaging device, and the adjustment can be performed while the workpiece is being sent. Paying attention to the fact that adjustment time is not required unlike the method, a fixed focus type imaging device is adopted as a means for capturing images.

Before the detected portion of the workpiece passes through the focal position of the image pickup device, how much deviation from the focal position of the image pickup device passes, that is, if the deviation amount of the passing position can be detected, the deviation amount is determined. By moving the position of the imaging device in advance by a distance and correcting the position, the detected portion of the work can always pass through the focal position of the imaging device, and such correction can be performed while the work is being transported ( The present invention was developed based on the idea that it can be performed during the pitch feed time.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a visual inspection system capable of capturing an image of a detected portion of a workpiece at high speed and with high accuracy and performing a visual inspection.

[0011]

According to a first aspect of the present invention, there is provided a work transfer means for transferring a work in a specific direction, and a focus is provided on a work transfer path of the work by the work transfer means. An imaging device having a constant focal length, and an imaging processing unit configured to capture an image of a detected portion of the work by the imaging device and perform image processing, and an appearance inspection system that inspects the appearance of the work.
Device moving means linked to the imaging device for reciprocating the imaging device along its optical axis direction;
A non-contact type displacement detection sensor that is arranged on the conveyance direction of the work in the conveyance direction upstream of the imaging device and detects a shift amount of a passing position of a detection portion of the work;
An imaging position correction unit that receives a signal from the displacement detection sensor and controls the device moving unit to move the imaging device in accordance with the amount of displacement. Here, the shift amount of the passing position of the detection part of the work means the shift amount from the position where the detection part of the work passes through the focal position of the imaging device when the detection part of the work passes. .

[0012] According to this configuration, when the work being conveyed by the work conveying means is located on the upstream side of the imaging device, the displacement of the passing position of the detection part of the work is brought into contact with the detection part of the work by the displacement detection sensor. Without being detected.

[0013] Then, upon receiving a signal from the displacement detection sensor, the moving means is controlled by the imaging position correcting means, and the imaging device moves along the optical axis direction thereof. Is adjusted. That is, if the passing position of the detected part of the workpiece is shifted from the reference passing position (the position where the position correction of the imaging device is not necessary), the amount of the shift is detected, and the position of the imaging device is determined according to the amount of the shift. Is adjusted by being displaced in either direction, so that the detection site of the workpiece passes through the focal position of the imaging device. Therefore, the image of the detected part of the workpiece is accurately captured by the imaging device having a constant focal length, and the appearance inspection can be performed at high speed and with high accuracy.

Therefore, even if the detected part of the work is fluctuated in the moving direction (position correction direction) of the imaging device, the position of the image pickup device is corrected using the amount of the change as the amount of deviation, so that the detected part of the work is detected. Is accurately captured with focus always on. Therefore, for example, dust,
In the case where adhesion of fluff or the like, or stains such as fingerprints, release agents, and residual solvents is not allowed, it is precisely checked by inspection that there is no such adhesion or stain.

It is preferable that the imaging position correcting means has a depth of field of the imaging device as a dead zone in which the imaging device is not moved. Here, the depth of field of the imaging device specifically means the depth of field determined by the optical system of the imaging device.

According to this configuration, since the depth of field of the imaging device is set as the dead zone, frequent movement of the imaging device can be avoided by adjusting the position of the imaging device.

According to a third aspect of the present invention, a position detecting means for detecting a current position of the work is linked to the work transfer means, and the image pickup position correcting means is configured to receive a signal from the displacement detection sensor. The apparatus may be configured to receive a signal from the position detecting means and control the device moving means in consideration of a change in the current position of the work.

With this configuration, the current position of the work on the transport path is accurately detected by the position detecting means,
In consideration of the change of the current position of the work, the device moving means is controlled by the imaging position correcting means,
Appearance inspection with higher accuracy becomes possible.

According to a fourth aspect of the present invention, the work includes:
When the detection part is long in the work transfer direction,
The irregularities of the detection portion in the longitudinal direction (transport direction) of the workpiece tend to be large, and the inventions of claims 1 to 3 are particularly effective.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of a visual inspection system according to the present invention, FIG. 2 is a front view showing an example of a work inspected by the visual inspection system according to the present invention, and FIG. It is.

FIG. 1 shows a visual inspection system 1 according to the present invention.
As shown in (1), a work transfer device (not shown) that transfers the work W in a specific direction A, and an imaging in which the focus is located on the transfer path of the work W by the work transfer device and the focal length is constant (fixed) A CCD camera 2 which is a device, and an image processing apparatus 3 (for example, Keyence Corporation) which captures an image of a detected portion (surface) of the work W by taking an image of the detected portion (surface) by the CCD camera 2 and processes the detected portion of the work W. Image sensor CV-5 with built-in high-speed and high-precision monitor
00)), and the appearance (detection site) of the work W.
Is inspected at a high speed while transporting it. The optical axis of the CCD camera 2 is orthogonal to the transport path of the work W. Further, the work transfer device feeds the pitch in the visual field width of the CCD camera 2, and an image is captured once by the CCD camera 2 for each pitch feed.

As shown in FIGS. 2 and 3, the work W is formed as an integral part by bonding and fixing a rubber member W2 to a core metal W1 by using an adhesive W3. On the surface (detection site) of the rubber member W2,
Since scratches, dents, and air bubbles are not allowed, and the adhesive is not allowed to protrude in the area S2, the presence or absence of the adhesive is checked by checking an image obtained by image processing using the visual inspection system 1. You.

The CCD camera 2 of the visual inspection system 1
A moving device 4 (device moving means) which can move the CCD camera 2 in the optical axis direction to change the position thereof is linked to the CCD camera 2 and transports the CCD camera 2 and a work W (detection site). The distance to the route can be adjusted.

The moving device 4 has a motor 4a and a feed screw 4b which is driven to rotate by the motor 4a. The distal end of the feed screw 4b has a female screw (see FIG. 1) provided on the CCD camera 2 side. (Not shown).
Therefore, the moving device 4 controls the drive of the motor 4 to adjust the rotation amount of the feed screw bar 4b, thereby adjusting the distance that the female screw portion moves with respect to the screw bar 4b. Since the CCD camera 2 also moves by the movement of the female screw portion, the CCD camera 2 moves.
The imaging position of the camera 2 is adjusted with high accuracy.
With this adjustment, the detection portion of the work W is moved to the CCD camera 2.
, And the accuracy of capturing an image of the detected portion of the workpiece W is improved.

The moving device 4 converts the rotational motion of the motor 4a into the linear motion of the CCD camera 2 (the feed screw rod 4b).
Therefore, it is also possible to use a linear motor or an ultrasonic motor (piezoelectric motor).

A non-contact type displacement detection sensor 5 (for example, for detecting a shift amount of a passing position of a detection portion of the work W) is provided upstream of the CCD camera 2 in the conveyance direction of the work W in the conveyance direction. And an ultra-high precision laser displacement meter (LC) manufactured by KEYENCE CORPORATION. Here, the deviation amount of the passing position is a deviation from a reference position such that when the detection portion of the work W passes, the detection portion of the work W passes through the focal position of the CCD camera 2 as described above. Quantity. Therefore, if the detection portion of the work W passes through the reference position near the transport path where the displacement detection sensor 5 is provided, the detection portion passes through the focal position on the optical axis of the CCD camera 2, so that the CCD No correction of the position of the camera 2 is necessary.

This displacement detection sensor 5 detects the distance P1 between the displacement detection sensor 5 and the detection site of the work W when the work W passes through a position facing the displacement W by non-contact measurement. The detected distance P1
And the reference distance, which is the distance between the displacement detection sensor 5 and the reference position, is the shift amount of the passing position, and corresponds to the correction amount (movement amount) of the CCD camera 2 as described later. That is, if the detection portion of the work W passes through a position where the distance from the displacement detection sensor 5 is a reference distance (if the distance P1 is equal to the reference distance), the CCD
When the camera 2 is at the initial position, the CCD camera 2
In this case, the detection portion of the work W can be detected by the CCD camera 2 without causing defocus. In FIG. 1, a distance P2 is a focal length of the CCD camera 2.

The displacement detecting sensor 5 is linked to a sequencer 6 functioning as an image pickup position correcting means.
The sequencer 6 receives a signal from the displacement detection sensor 5, controls the moving device 4 according to the detection result, adjusts the rotation amount of the feed screw rod 4b, and adjusts the CCD camera 2 to the displacement amount. Is moved by the position correction distance Pm corresponding to

The sequencer 6 is provided with the CCD
The configuration is such that the depth of field Pf of the camera 2 is provided as a dead zone in which the CCD camera 2 is not moved. Therefore, if the shift amount is within the depth of field Pf, CC
The position of the D camera 2 is not corrected, and the control at the time of position adjustment of the CCD camera 2 prevents the CCD camera 2 from frequently moving for position adjustment.

According to the above-mentioned apparatus, the work W is pitch-fed by the conveying device (not shown) with the visual field width of the CCD camera 2, and the image is taken in over the entire length of the work W by a plurality of feeds. Is inspected.

Then, the transferred workpiece W is CC
On the upstream side of the D camera 2, first, when the work W passes in front of the displacement detection sensor 5, the work W
Is detected (measured) by the displacement detection sensor 5 without damaging the detection portion of the workpiece W (non-contact measurement).

The displacement of the passing position, which is the difference between the distance P1 and the reference distance, is obtained by the sequencer 6 which receives the signal from the displacement detection sensor 5, and the moving device 4 is driven according to the displacement, and the CCD is driven. The position of the camera 2 is adjusted, and the distance between the CCD camera 2 and the transport path of the detection portion of the work W is adjusted.

That is, if the distance P1 detected by the displacement detecting sensor 5 is different from the reference distance, during the pitch feed time (while the workpiece W is moving).
Then, the position of the CCD camera 2 is adjusted by moving the CCD camera 2 in any direction on the optical axis of the CCD camera 2 in accordance with the shift amount. Such position adjustment is performed by CCD
Since the camera 2 is of a fixed focus type in which the focal length is fixed, the position of the entirety of the CCD camera 2 is corrected so that the detected portion of the work W always passes through the focal position of the CCD camera 2. It is. Also, during the feed time of the pitch feed (while the workpiece W is moving),
The reason for moving the CCD camera 2 according to the displacement amount is as follows.
This is to avoid waiting for the inspection during the position adjustment and to speed up the inspection.

In other words, on the upstream side of the CCD camera 2, the shift amount of the detection portion of the work W is detected in advance,
Utilizing the feed time of the pitch feed until the center of the detection portion of the work W reaches the optical axis of the CCD camera 2 and is photographed, the detection portion of the work W passes through the focal position of the CCD camera 2. In addition, the position of the CCD camera 2 in the optical axis direction is adjusted, so that the detection position of the work W is always focused when the CCD camera 2 captures an image.

Therefore, even if the detected portion of the work W has irregularities (surface properties, roughness) in the moving direction (optical axis direction) of the CCD camera 2, the irregularities are corrected as the shift amount, and the CCD When an image is taken by the camera 2, an image is captured with high accuracy. The inspection system according to the present invention is particularly effective because such irregularities in the transport direction of the workpiece W tend to be particularly large when the detection site is a long object that is long in the workpiece transport direction.

Further, since the depth of field Pf of the CD camera 2 is set as the dead zone, the control at the time of position adjustment of the CCD camera 2 causes the CCD camera 2 to frequently move for position adjustment in the optical axis direction. Is avoided.

In the above-described embodiment, when the workpiece W passes in front of the displacement detection sensor 5, the shift amount of the passing position of the detection portion of the workpiece W is detected, and C
The position of the CD camera 2 is merely adjusted, but if it is desired to increase the inspection accuracy depending on the transfer speed and the degree of dimensional accuracy, the work transfer means detects the current position of the work W by the work transfer means. The sequencer 6 (imaging position correcting means) receives a signal from the position detecting means in addition to a signal from the displacement detecting sensor 5 and takes into account a change in the current position of the work W. Then, the driving device 4 may be controlled.

In this way, the work W on the transport path
Is accurately detected by the position detecting means, and the driving device 4 is controlled by the sequencer 6 in consideration of a change in the current position of the work W, so that the appearance inspection can be performed with higher accuracy. Become. That is, the specific range of the detection site of the work W whose displacement has been measured in advance is
When capturing an image with the CCD camera 2 whose position has been corrected according to the shift amount, it is possible to increase the accuracy with which the visual field range captured by the CCD camera 2 matches the specific range.

In the above-described embodiment, the pitch is used as the transporting mode. However, the present invention is not limited to this. For example, when the processing speed of the entire system is high, the transporting is performed within the response range. It is also possible to set a constant speed feed.

[0041]

The present invention is embodied as described above, and has the following effects.

According to a first aspect of the present invention, the position of the image pickup device is adjusted according to the amount of deviation of the passing position of the detection part of the work,
Since an image of a work is captured and inspected by an imaging device having a unique focal length, even if the detected portion of the work fluctuates due to irregularities or the like in the moving direction of the imaging device, the fluctuation does not occur. The position of the imaging device can be adjusted by using the amount as a shift amount, and a portion to be imaged by the imaging device can be accurately imaged and captured as image processing data. Therefore, the appearance inspection can be performed at high speed and with high accuracy.

If the imaging position correcting means has the depth of field of the imaging device as a dead zone in which the imaging device is not moved, the position of the imaging device is adjusted. At this time, it is possible to prevent the position of the imaging device from being frequently controlled and moved.

According to a third aspect of the present invention, a position detecting means for detecting a current position of the work is linked to the work transporting means, and the imaging position correcting means adds the signal from the displacement detecting sensor. By receiving a signal from the position detecting means and controlling the device moving means in consideration of a change in the current position of the work, the current position of the work on the transport path can be accurately detected. Therefore, the device moving means can be controlled by the imaging position correcting means in consideration of the change in the current position of the work, and the appearance inspection can be performed with higher accuracy.

According to a fourth aspect of the present invention, the work includes:
When the detection portion is long in the work transfer direction, the unevenness in the work transfer direction (longitudinal direction) tends to be large, which is particularly effective for the inventions of claims 1 to 3.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a visual inspection system according to the present invention.

FIG. 2 is a front view showing an example of a workpiece inspected by the visual inspection system according to the present invention.

FIG. 3 is an enlarged side view of the same.

[Explanation of symbols]

Reference Signs List 1 visual inspection system 2 CCD camera (imaging device) 3 image processing device 4 moving device (device moving means) 4a motor 4b feed screw rod 5 non-contact displacement detection sensor 6 sequencer (imaging position correcting means) W work W1 core metal W2 Rubber member P1 Distance between displacement detection sensor 5 and detection site of workpiece W P2 Focal length of CCD camera 2 Pf Depth of field of CCD camera 2 Pm Position correction distance of CCD camera 2

Claims (4)

[Claims] 1. A work transfer means for transferring a work in a specific direction, an image pickup device having a fixed focal length in a work transfer path by the work transfer means, and a detection of the work by the image pickup device. An image processing means for taking an image of a part and performing image processing, wherein the appearance inspection system inspects the appearance of the work, and is linked to the imaging device to reciprocate the imaging device along an optical axis direction thereof. A non-contact type displacement detection sensor disposed on the conveyance path of the work upstream of the imaging device in the conveyance direction to detect a shift amount of a passing position of a detection part of the work; An imaging position for receiving the signal from the sensor and controlling the device moving means to move the imaging device in accordance with the shift amount; An appearance inspection system comprising: a position correction unit. 2. The visual inspection system according to claim 1, wherein the imaging position correction unit has a depth of field of the imaging device as a dead zone in which the imaging device is not moved. 3. The work transfer means is linked with a position detection means for detecting a current position of the work, and the imaging position correction means adds a signal from the displacement detection sensor to a signal from the position detection means. The visual inspection system according to claim 1, wherein a signal is received, and the device moving unit is controlled in consideration of a change in a current position of the work. 4. The visual inspection system according to claim 1, wherein the workpiece has a long detection part in a transport direction of the workpiece.